<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<script language="javascript">
//页面加载时，生成随机验证码
	window.onload=function(){
	 createCode(4);    
	}
	
	//生成验证码的方法
	function createCode(length) {
		var code = "";
		var codeLength = parseInt(length); //验证码的长度
		var checkCode = document.getElementById("checkCode");
		////所有候选组成验证码的字符，当然也可以用中文的
		var codeChars = new Array(0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
		'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',
		'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'); 
		//循环组成验证码的字符串
		for (var i = 0; i < codeLength; i++)
		{
			//获取随机验证码下标
			var charNum = Math.floor(Math.random() * 62);
			//组合成指定字符验证码
			code += codeChars[charNum];
		}
		if (checkCode)
		{
			//为验证码区域添加样式名
			checkCode.className = "code";
			//将生成验证码赋值到显示区
			checkCode.innerHTML = code;
		}
	}
	
	//检查验证码是否正确
	function validateCode()
	{
		//获取显示区生成的验证码
		var checkCode = document.getElementById("checkCode").innerHTML;
		//获取输入的验证码
		var inputCode = document.getElementById("inputCode").value;
		console.log(checkCode);
		console.log(inputCode);
		if (inputCode.length <= 0)
		{
			alert("请输入验证码！");
		}
		else if (inputCode.toUpperCase() != checkCode.toUpperCase())
		{
			alert("验证码输入有误！");
			createCode(4);
		}
		else
		{
			alert("验证码正确！");
		}       
	}
</script>
</head>


<body>
<tr>
    	<td>验证码</td>
    	<td ><input type="text" id="inputCode" size="5" name="yzm"/></td>
        <td><div id="checkCode" class="code" onclick="createCode(4)" ></div></td>
    </tr>


 <tr>
       <td>验证码</td>
    <td><label for="textfield4"></label>
      <input width="100px" height="20px" type="text" name="yzm" id="textfield4"> <label for="textfield5"></label>
      <input name="textfield5" type="text" id="textfield5" readonly width="100px" height="100px"></td>
  </tr>
  </body>